The invention relates to platelet activation proteins.
The normal hemostatic system regulates bleeding and thrombosis through a series of complex interactions between components of the blood vessel wall, circulating blood platelets, and plasma proteins.
Because vascular injury causes a rapid loss of the protein, fluid, and cellular components of the blood, animals have developed rapid responses to patch the vessel and initiate its repair. These rapid responses are initiated by the platelet, a highly specialized cell that reacts to vascular injury. Normally, platelets circulate in the blood as quiescent and nonadherent cells, monitoring the integrity of the blood vessel. In response to vascular injury, platelets adhere to de-endothelialized areas and activate. Platelet activation induces profound morphologic and functional changes in the cell. Platelets change shape, aggregate with other platelets, and adhere to other cells. With full activation, platelets secrete the contents of their lysosomal, alpha, and dense granules, thereby expressing adhesion molecules, growth factors, coagulation enzymes, and other specialized molecules. Molecules expressed by activated platelets execute many of the complex cellular and biochemical processes that staunch the loss of blood and begin the process of vascular repair.
The cellular and biochemical processes initiated by platelets in response to vascular injury can be lifesaving, but in the absence of such injury these same processes can be deleterious. For example, unregulated arterial platelet thrombosis can occlude the blood supply to organs and lead to strokes, heart attacks, and limb necrosis.